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 * Copyright (c) 2014, Oracle America, Inc.

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package org.openjdk.jmh.samples;


import org.openjdk.jmh.annotations.Benchmark;

import org.openjdk.jmh.annotations.Group;

import org.openjdk.jmh.annotations.Scope;

import org.openjdk.jmh.annotations.State;

import org.openjdk.jmh.infra.Control;

import org.openjdk.jmh.runner.Runner;

import org.openjdk.jmh.runner.RunnerException;

import org.openjdk.jmh.runner.options.Options;

import org.openjdk.jmh.runner.options.OptionsBuilder;


import java.util.concurrent.atomic.AtomicBoolean;


@State(Scope.Group)

public class JMHSample_18_Control {


 /*

  * Sometimes you need the tap into the harness mind to get the info

  * on the transition change. For this, we have the experimental state object,

  * Control, which is updated by JMH as we go.

  */


 /*

  * In this example, we want to estimate the ping-pong speed for the simple

  * AtomicBoolean. Unfortunately, doing that in naive manner will livelock

  * one of the threads, because the executions of ping/pong are not paired

  * perfectly. We need the escape hatch to terminate the loop if threads

  * are about to leave the measurement.

  */


 public final AtomicBoolean flag = new AtomicBoolean();


 @Benchmark

 @Group("pingpong")

 public void ping(Control cnt) {

  while (!cnt.stopMeasurement && !flag.compareAndSet(false, true)) {

   // this body is intentionally left blank

  }

 }


 @Benchmark

 @Group("pingpong")

 public void pong(Control cnt) {

  while (!cnt.stopMeasurement && !flag.compareAndSet(true, false)) {

   // this body is intentionally left blank

  }

 }


 /*

  * ============================== HOW TO RUN THIS TEST: ====================================

  *

  * You can run this test:

  *

  * a) Via the command line:

  *    $ mvn clean install

  *    $ java -jar target/benchmarks.jar JMHSample_18 -t 2 -f 1

  *    (we requested 2 threads and single fork; there are also other options, see -h)

  *

  * b) Via the Java API:

  *    (see the JMH homepage for possible caveats when running from IDE:

  *      http://openjdk.java.net/projects/code-tools/jmh/)

  */


 public static void main(String[] args) throws RunnerException {

  Options opt = new OptionsBuilder()

          .include(JMHSample_18_Control.class.getSimpleName())

          .threads(2)

          .forks(1)

          .build();


  new Runner(opt).run();

 }
// 本例介绍了使用 Control 的场景
// 如果测试一个线程组对一个AtomicBoolean分别进行set true 和 set false操作，我们知道只有一个线程set true成功，另一个线程才能对其set false，否则另一个线程就陷入死锁，但我们的测试用例两个方法的执行不是均匀成对的，所以极大概率测试会陷入死锁，这时需要JMH提供的Control进行控制，当测量结束，双方都退出循环。
}

